In the past, boring tools for use with numerically controlled machine tools have been known. The boring tool is typically used when it is necessary to machine a cylindrical opening in a block of metal so that a finished, machined part can be provided. Generally speaking, a boring tool is different from a drilling tool: the drilling tool a removes metal to define a generally cylindrical opening in the part; whereas, the boring tool operates on an existing cylindrical opening to create a finished opening which has much better tolerances on roundness of the opening and cylindricalness of the opening.
In some cases, the bore must be perfectly cylindrical from one end to the other. In other cases, the bore has changes in its diameter at predetermined locations along the length of the bore. One very common example of such a change in diameter is a counterbore at the entrance to the opening.
In order for a boring tool to be useful in a machine tool so that the boring tool can machine a cylindrical bore with the necessary diameters and tolerances, it is of course necessary that such a boring tool be capable of very accurate adjustment in both the axial direction (along the longitudinal axis of the boring tool) and in the radial direction.
In the past, suitable boring tools have been carefully machined with a high degree of precision in longitudinal and radial adjustability. For example, it is known to carefully machine a generally square piece of material with a rectangular bore extending longitudinally and essentially tangential to a transverse slot in which a tool bar is slidable received. The rectangular bore receives a wedge assembly which includes a wedge and closely fitted bearing shoes which guide the wedge during longitudinal movement. Longitudinal movement of the wedge is transformed into radial movement of the tool bar through cooperation of splines on the wedge with splines on the tool bar.
Control on the accuracy of movement of the tool bar depends on the precision with which the cooperating splines can be fitted together. Moreover, to the extent that precise fitting of the splines is not obtained, unacceptable tolerances will rapidly develop as a result of wear caused by use of the tool.
In addition to such alignment problems, known boring tools require a large number of pieces each of which requires precise machining. For example, the tool body itself is often machined as is the wedge, its guides, the tool bar and cooperating structures. As is well known, the expense of producing any part is a function of the number and precision of machining operations which are required to make the part. Accordingly, the known boring tools are known to be economically expensive.
It would, naturally, be advantageous to have a boring tool in which alignment of the driving splines could be accurately controlled during manufacture. In like fashion, it would be advantageous to have a boring tool in which the number of precision machining operations could be significantly reduced so that the boring tool could be manufactured more economically.
Accordingly, it is seen that the need continues to exist for a new boring tool which overcomes problems of the type discussed above.